"Please let us know if we can be of further assistance," wrote former assistant attorney general Jay Bybee at the end of his 2002 memo [PDF] for the Central Intelligence Agency. It's hard to imagine how much more assistance he could have offered the CIA. Bybee gave the CIA the legal equivalent of a blank cheque to walk over a moral boundary defined by the Geneva Convention, Article 16 of the UN Charter, the Convention Against Torture, as well as section 2340 of the United States Code.

Today President Obama opened the door to prosecuting the authors of these torture memos. Americans must consider doing more than shaking their heads in disapproval. Instead, concrete action should be taken to prevent this from ever happening again and to restore a sense of justice across the land.

The "Bybee memo" is hardly unique, insofar as it was a part of several legal opinions written by the White House's office of legal counsel (OLC) under George Bush, which included the infamous memo by John Yoo. But the fact that the author of this memo went on to receive a lifetime appointment to the ninth circuit bears special attention by Congress and the American people. Although some Obama officials have expressed a desire to move past this dark chapter in American history, it is hard to ignore the fact that Bybee will be permitted to have a lasting impact on constitutional interpretation from his seat as a federal judge on the ninth circuit - the largest of the federal appeals courts and only a rung below the supreme court in the US legal system. We cannot overlook the past, because it is a blueprint for the future.

A close examination of the Bybee memo reveals a man who was willing to abandon all legal ethics to achieve a result that his client wanted, with total disregard for the values of America and the rule of law he swore an oath to protect as a White House assistant attorney general. In a careful and deliberate manner Bybee dismantled any common sense understanding of the word "torture" and paved the way for Khalid Sheikh Mohammad to be waterboarded 183 times in concert with twelve other methods of "enhanced" interrogation, including sleep deprivation up to 180 hours, "walling," and forced nudity.

The general strategy of Bybee's memo was to create doubt where there should be none, and to erode the plain meaning of the term "torture" so that it appeared grey and defensible for any CIA operative relying on his legal conclusions in good faith. With legal manoeuvre, Bybee turns morality on its head and suggests that simulating drowning does not produce the physical or mental severity contemplated by section 2340 of the federal prohibition on torture. He writes that "torture is at the furthest end of impermissible actions" and goes on to separate torture from "cruel, inhuman, or degrading treatment or punishment," which he calls a "lower level" of actions.

Bybee says that interrogation techniques that produce "prolonged mental harm", like post-traumatic stress disorder, would be torture, but waterboarding would not produce this effect. It's hard to imagine that simulated drownings would not produce a lasting psychological effect on its recipient. But even if they do, Bybee says all that a CIA operative need to assert is that he had a good faith belief it would not produce a lasting effect. He even suggests waterboarding could be a form of self-defense by a CIA operative, which goes against centuries of law which require that self-defense claims have an imminent threat of harm rather than an abstract idea of harm.

Russian roulette, he opines, creates a threat of imminent death that constitutes torture, but waterboarding does not meet the dictionary definition of "severe pain" or "suffering" because there is no organ failure or impairment of bodily function. The logic is absurd, but because section 2340 requires that the individual accused of torture "intend" to torture, the existence of the memo serves as cover for any operatives actions who could not intend to do what Bybee specifically told them was not torture under the law. He suggested that torturing by accident is analogous to someone who accidentally commits mail fraud but does not realize what was in the mail they sent. Bybee sought to make it less obvious that enhanced interrogation is "clearly established" to be prohibited under section 2304. What's worse, his analysis serves to assuage the conscious which should have been troubled by such techniques.

Memos such as the one written by Judge Bybee created the moral approval for torture in the minds of the CIA and Bush administration. Everything became subjective and therefore reasonable from a certain point of view. Bybee gave the stamp of approval to inexcusable conduct and created a permissive atmosphere that let anything go. Unfortunately, as CS Lewis once observed, "those who torment us for our own good will torment us without end, for they do so with the approval of their own conscience."

In a separate OLC memo released by President Obama, the stark details of enhanced interrogation techniques become apparent. Despite repeated suggestions that waterboarding does not constitute physical or mental harm, the 2005 memo suggests that detainees suffer psychological resignation, vomiting and spasms of the larynx. But to cover their final conclusions that the OLC advice was sound, the memo goes on to say that "our conclusions depend" on the assessments by CIA approved psychologists and the CIA office of medical services. Everyone has everyone else covered. These later memos do not even admit that techniques which go beyond their limitations are illegal, saying only that the OLC "express[es] no view" on whether sleep deprivation in excess of 180 hours violates the law. It is clear that memos like the one authored by Judge Bybee contributed to a lawless and immoral culture in the Bush administration that undermined the US's ability to advance human rights around the world and on a more fundamental level to be considered a moral leader and civilized nation.

The question before the American people is not only whether Bybee should go to jail for writing his opinion, but whether he is fit to serve as a federal judge. It is not the job of the attorney general's office to be an advocate for brutality and conform its analysis to the end the CIA seeks to achieve, but to craft legal opinions that uphold the rule of law. It it is true that at times these rights apply to even the most despicable of people, but that is the price of a free society. Our enemies are not bound by such restrictions but as President Obama told the CIA on Monday, that is what is supposed to make America different from those we are fighting.

Sadly, it is questionable that even these techniques were used to extract intelligence, given that they were applied 183 times to Khalid Sheikh Mohammad in one month, and 83 times to Abu Zubaydah. The 2005 Bradbury memo makes clear that the goal of watebroarding is designed to encourage cooperation so as to "avoid future sessions" and to create a mindset in detainees that they must protect themselves more than their information. But if it took 183 times to create cooperation, or if waterboarding was done despite cooperation, this naturally leads one to wonder whether the techniques were designed as retribution for 9/11 instead of being performed to avert a future attack. It's impossible to know the intent of those who waterboarded, and with the CIA tapes of the interrogations conveniently destroyed we may never know.

As much as we need to look to the future, Americans cannot "un-know" what we now recognise our government has done in the name of preserving our liberty. The real damage that lawyers like Judge Bybee have done to our nation were best expressed by US Army prosecutor Major Michael Holley in his closing arguments regarding Abu Ghraib: "If a prisoner… believes that he will be humiliated and subjected to degrading treatment, why wouldn't he continue to fight until the last breath? And in fighting, might he not take the lives of soldiers, lives that might not otherwise be spent? This type of behavior has long-term impact."

Unfortunately, the impact of Judge Bybee's tenure on the US legal system may be longer and more enduring than the stain of torture on our nation's image around the world. Even if Obama's attorney general Eric Holder decides not to prosecute Bybee, at least he should not be permitted to retain his lifetime appointment to any court where justice is to be found.